Grinding machine

ABSTRACT

A grinding machine having a bed, workpiece supporting means, a wheel slide rotatably supporting a grinding wheel, a dresser for dressing the grinding wheel, and dresser feed means for feeding the dresser toward the grinding wheel by a predetermined dressing amount whenever a dressing operation is requested includes original position determination means having shiftable means supported on the wheel slide and movable together with the same, drive means serving to move the shiftable means by an amount corresponding to the predetermined dressing amount in a direction of retraction of the wheel slide whenever the dressing operation on the grinding wheel is performed, and means for detecting an original position of the wheel slide in co-operation with the shiftable means and generating a signal serving to stop the movement of the wheel slide, whereby the wheel slide can be accurately positioned at the original position thereof which must be varied in accordance with a reduction of the grinding wheel by dressing operations thereon.

[ 1 GRINDING MACHINE [75] Inventors: Hiroshi Ota, Kariya; Tetsuo Matsuzaki, Nishio, both of Japan [73] Assignee: Toyoda-Koki Kabushiki Kaisha,

Japan [22} Filed: Oct. 29, 1973 [21] Appl. No: 410,555

[30] Foreign Application Priority Data Oct. 28, 1972 Japan 47-108218 [52] U.S. Cl 51/5 D; 51/1658; 5l/l65.87 [51} Int. Cl B24b 51/00 [58] Field of Search 51/5 D, 165 R, 165.87,

[56] References Cited UNITED STATES PATENTS 2,634,556 4/1953 Aeppli 51/5 D 2,929,172 3/1960 Pasell 5l/l65r87 X 2,969,625 1/1961 Snyderm, 5l/l65.87 3,717,961 2/1973 Suzuki .4 5l/l65.88 3,721,047 3/1973 Ryan .r 51/l65.87 X

37 W /4 I5 19/? f7 1 May 27, 1975 Primary Examiner-Harold D Whitehead Attorney, Agent, or FirmOblon, Fisher, Spivak, McClelland & Maier [57} ABSTRACT A grinding machine having a bed, workpiece supporting means, a wheel slide rotatably supporting a grinding wheel, a dresser for dressing the grinding wheel, and dresser feed means for feeding the dresser toward the grinding wheel by a predetermined dressing amount whenever a dressing operation is requested includes original position determination means having shiftable means supported on the wheel slide and movable together with the same, drive means serving to move the shiftable means by an amount corresponding to the predetermined dressing amount in a direction of retraction of the wheel slide whenever the dressing operation on the grinding wheel is performed, and means for detecting an original position of the wheel slide in cooperation with the shiftable means and generating a signal serving to stop the movement of the wheel slide, whereby the wheel slide can be accurately positioned at the original position thereof which must be varied in accordance with a reduction of the grinding wheel by dressing operations thereon.

11 Claims, 3 Drawing Figures Iii GRINDING MACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a grinding machine and more particularly to an improved grinding machine having an original position determination device.

2. Description of the Prior Art In a conventional grinding machine, for example, in which the infeed of a wheel slide is numerically controlled by a stepping motor, there is a defect wherein it is vertually impossible to return the wheel slide to an original position which is varied in accordance with a reduction of the diameter of the grinding wheel through dressing or trueing operations thereon if the electric current is cut off or an emergency stop is performed in the course of a grinding operation because the content of a counter which records the amount of infeed of the wheel slide is cleared and a memory on energization of magnetic phase of a stepping motor drive unit is faded away.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved grinding machine having an Orlgmal position determination device which is capable f memorizing the exact original position of the wheel slide or the grinding surface of the grinding wheel.

Another object of the present invention is the provi- SlOll of an original position determination device which has a simple construction and is therefore capable of bemg ily produced at low cost.

The foregoing and other objects are obtained in aceordance with one aspect of the present invention thmugh e provision of a grinding machine having a workpiece supporting means mounted on the bed; wheel slide means slidably mounted on the bed and rotambli/ pporting at least one grinding wheel rotated y a motor; wheel slide actuating means for moving the wheel slide means toward and away from the. Wflfk- P grinding wheel dressing means being movab toward and away from the grinding wheel for dressing the same; dresser feed means for feeding the grinding whee] dressing means toward the grinding wheel by a predetermined dressing amount whenever a dressing opeianon the rinding wheel is required; dresser acwatmg eans for moving the grinding wheel dressing means so as to be able to perform a dressing operat f the grinding heel; and original position determinan means having shiftable means supported on the Wheel slide means and movable together with the same. drive means serving to move the shiftable means by an amount F ponding to the predetermined dressin amount in a direction of retraction of the wheel slide means whenever the dressing operation on th grinding Fl 18 performed, and means for detecting an or P Q Of the wheel slide means in cooperation with the sh|ftable means and generating a signal serving to p the movement of the wheel slide means, whereby heel slide means can be accurately positioned at the ongma' P sition thereof which must be varied in ccordance with a reduction of the grinding wheel y dressmg perations thereon.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects. features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of a preferred embodiment of the present invention when considered in connection with the accompanying drawings in which:

FIG. 1 is a cross-section view of a feed mechanism of a grinding machine adopting the present invention;

FIG. 2 is a part view, partly in section, of a grinding machine embodying the subject matter of the present invention; and

FIG. 3 is a sectional view taken along the line Ill-Ill of FIG. 2.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, wherein like reference characters designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, a grinding machine is shown having a bed 10, on which a stationary base 11 is fixedly mounted. A wheel slide 13 is slidably mounted on guide ways 12 which are formed on the upper surface of the base 11. The wheel slide 13 rotatably supports a grinding wheel spindle 15 having a grinding wheel 14, which spindle and grinding wheel are driven by a motor 16 through a belt 18 and pulleys l7, 19 respectively fixed on the motor 16 and the spindle 15. Furthermore, a rapid feed cylinder 20 is fixedly mounted on the base 11, and a piston 21 is slidably fitted in the cylinder 20. Through a bore 21a formed in the piston 21, a feed screw 22 is provided, which screw 22 is rotatable but is not movable in an axial direction thereof against the piston 21. The screw 22 is threadedly engaged with a nut 23 fixed on the under surface of the wheel slide 13. A gear 24 is securedly provided on an extension of the screw 22 which is extended out of the rear end of the piston 21 and on the end of the extension provided are dogs 25, 26 which cooperate with limit switches LS1, LS2, for respectively detecting an advanced end and a retracting end on the rapid feed movement. The gears 29, 30 are co-axially and fixedly mounted on a shaft 27 rotatably supported on the rear side of the base 11. Moreover, the gears 31, 32 are securedly provided on a shaft 28 rotatably mounted on the same side of the base 11. The gear 24 is engaged with the gear 29 and is slidable thereon. The gears 30 and 32 are respectively engaged with the gears 31 and 34, which gear 34 is provided and secured on a drive shaft of a stepping motor 33. On the above noted bed 9 guide ays 35, 35 are formed in a direction perpendrcular to the guide ways 12, and a traverse table 36 is slldably guided thereon. A swivel table 38 supporting a work head 37 and a tail stock (not shown) is pivotally mounted on the traverse table 36. The traverse table 36 can be moved or driven by a cylinder device 39 secured on the bed 10. It is to be noted that a grinding wheel dressing device, which will be later described, is proytded on the wheel slide 13, and the grinding wheel 14 t8 dressed by the dresser through an infeed of a rotary dressfir y a predetermined unit distance against a lg Surface of the grinding wheel. Thus, the com- Pensatloh 0f he position of the wheel slide 13 is performed henever the dressing operation on the grindmg Wheel 14 is Performed, that is, the wheel slide 13 is mmpensiltcd y e stepping motor 33 corresponding (655mg amount before the start of a grinding operatlOfl ene er the dressing operation is performed. In

addition, an up-down counter is adopted for controlling the infeed amount of the wheel slide 13.

Referring now to FIG. 2, a rotary dressing device and an original position determination device are shown. The numeral 40 shows a base body of the rotary dressing device fixed on the wheel slide 13, and in which base body a dresser supporting ram 41 is mounted and is slidable in an axial direction thereof against the grinding wheel 14. The rotation of the ram is limited by the key 42. On the front end of the ram 41, a supporting member 43 is fixedly provided and rotatably supports a rotary dresser 44 which can be driven by a hydraulic motor 45 mounted on the supporting member 43. On the rear end of the base body 40, a gear box 40 is mounted and furthermore, a cylinder block 48 provided with a cylinder bore 47 is fixedly mounted on the rear end of the gear box 46. The above noted cylinder is provided for a rapid advance of the dressing device. Moreover, a piston 49 slidably mounted on the cylinder bore 47 rotatably supports one end of a feed shaft 50. A screw 500 formed on another end of the feed shaft 50 is engaged with a female screw formed in one end of a sleeve which is rotatably supported in the ram 41 but which is not axially movable relative to the ram. The ram 41 supporting the rotary dresser 44 is, therefore, rapidly movable toward and away from the grinding wheel in accordance with the actuation of the cylinder mechanism 47, 48, 49 for the rapid feed movement.

A gear 52 is securedly mounted on the feed shaft 50 and is connected to a rack and piston mechanism (not shown in Figures) through a gear train having a worm gear and worm wheel (not shown). The gear 52 can be rotated in a clockwise and a counter clockwise direc tion by a predetermined amount in response to for wardly and backwardly reciprocal actuations of the rack and piston mechanism. In accordance with the rotation of the gear 52, the feed shaft 50, with the screw 50a, is rotated in a clockwise or counter clockwise direction and therefore, the ram 41 is moved in an axial direction thereof through the sleeve engaged with the screw 500. It should be noted that the foregoing movement of ram 41 is performed after the rapid advance thereof by actuation of the cylinder mechanism 47, 48, 49, Accordingly, the dresser 44 on the ram 41 can cut or dress the grinding wheel by a predetermined dressing amount or depth which was defined by an infeed means which will be later described. On the outer sur face of the sleeve 51, a recess 51a for a key engagement is formed in an axial direction thereof. A worm wheel 53 is provided coaxially to the sleeve and is rotatably mounted in the gear box 46. The worm wheel 53 is connected with the sleeve 51 through the key and is axially movable relative to the sleeve 51. Moreover, a rotary shaft 54 is rotatably mounted in the gear box 46 in par' allel to the feed shaft 50 and a worm wheel 55 of the same dimensions as the worm wheel 53 is securedly mounted on the shaft 54. As shown in FIGS. 2 and 3, these worm wheels 53, 54 are engaged with a worm 57 which is formed on one end of a worm shaft 56 rotatably mounted in the gear box 46. A bevel gear 58, fixedly mounted on another end of the worm shaft 56, is engaged with a bevel gear 59 which is connected to an infeed means 60 having an intermittent motion mechanism like a ratchet mechanism (not shown). It is to be noted that the infeed means 60 is usually actuated before the actuation of the rack piston mechanism serving to rotate the gear 52 and serves to rotate the worm shaft 56 by a predetermined value in each actuation thereof. By the rotation of the shaft 56 i.e., the worm 57, both worm wheels 53, 55. i.e., the sleeve 51 and the shaft 54 are synchronously rotated by a predetermined amount. Thus, the ram 41 with the dresser can be advanced by a predetermined small distance corresponding to a dressing amount or a grinding wheel removal previously to the infeed movement by the rotation of the gear 52. In addition, the ram 41 is quickly reversed to a starting position thereof by driving the worm shaft 56 by a motor (not shown), when the grinding wheel 14 is reduced to a predetermined limit diameter and is, therefore, to be changed to a fresh one having a predetermined large diameter.

The shaft 54 is provided with a screw 54a which is extended in a direction of a retraction of the wheel slide 13. The screw 54a is engaged with a nut 61 which is fixed on one end of a shaft 62 slidably mounted in the gear box 46. The pitch of the screw 54a is formed on the same as that of the feed screw 50a on the feed shaft 50, and therefore, the shaft 62 is shifted in a direction of retraction of the wheel slide 13 by a distance equal to the infeed amount of the ram 41, that is, to the dressing amount in each dressing operation. it is to be noted that the wheel slide 13 is compensated by the stepping motor 33 in response to the dressing amount, as is above noted, because the number of pulses applied to the stepping motor are predetermined corresponding to the mechanical infeed amount given by the infeed means 60. However, the shaft 62 can substantially be positioned at the original position thereof when the wheel slide 13 is existing at its nominal original position even if the position of the wheel slide 13 is compensated in response to the reduction of the grinding wheel diameter caused by the dressing operations, because the shaft 62 is backwardly shifted by a distance equal to the advancing distance by the compensation of the wheel slide position.

Another end of the shaft 62 is extended out of the gear box 46 and on this end, an original position indicating dog 63 is threadedly engaged and secured thereon, which dog serves to determine or detect the original position of the wheel slide or grinding wheel. Moreover, a supporting bracket 64 is secured on the rear end of the base 11 in a manner that the same 64 never prevents the retraction or backward movement of the wheel slide 13. On the bracket 64, at detecting box 65 is mounted. A lever 66 is rotatably pivoted by the pin 67 in the box 65, and is urged upwardly by a spring 69 provided between the same 66 and a supporting block 68 secured in the box 65 so that the lever 66 can be engaged with the dog 63. A position detector 70 is provided on the supporting block 68 and whenever the wheel slide 13 is positioned at the original position thereof, an original position detecting switch in the detector 70 is closed to actuate because a senser 70a of the detector 70 is depressed by the lever 66 which is engaged with the dog 63 and is therefore swung against the force of the spring 69.

In addition, a limit switch 71 for safety is provided in the box 65 and serves to generate a signal for an emergency retraction of the wheel slide 13 when the dog 63 depresses the limit switch 71 in case of an excessive advance of the wheel slide on account of, for example, a problem in a sizing device adopted in the grinding operation. Furthermore, the detector 70 has a slow down switch for a reduction of speed of the stepping motor 33, which switch is closed by the dog 63 before the above noted original position detecting switch is closed. The slow down signal generated, therefore serves to reduce the speed of the stepping motor 33 at a front point slightly before the original position in the course of the rapid retraction of the wheel slide by the stepping motor, which retraction is needed after a stoppage of electric current or an emergency stop of the wheel slide.

As above noted, the original position indicating dog 63 on the shaft 62 is shifted backwardly relative to the wheel shaft 13 by a distance equal to the compensating amount of the wheel slide, i.e., the dressing amount whenever the dressing operation is performed and so, the dog 63 necessarily depresses the sensor 700 of the detector 70 and therefore the original position detecting switch is enabled to work whenever the wheel slide 13 is returned to the original position which is gradually changed. That is, the grinding surface of the grinding wheel is returned to the original position which is a fixed point. However, in the course of normal grinding cycles, the original position detecting signal generated from the detector 70 is not utilized because a reversible counter, in which the advanced distance of the wheel slide 13 is added up, serves to control the retraction movement of the wheel slide 13 so that the retraction is stopped when the content of the reversible counter is reduced to zero.

When the stoppage of electrical current or the emergency stop occurs and it is therefore necessary to return the wheel slide to the original position thereof because a memory on the present position of the wheel slide 13 is cleared, a push button (not shown) for the retraction is depressed. By this operation at first, the wheel slide is rapidly moved by the rapid feed cylinder in FIG. 1. When the completion of the retraction of the piston 21 is detected by the limit switch LS2, the stepping motor 33 is driven in a counter clockwise direction and therefore the wheel slide 13 is continuously reversed at a rapid speed by the driving pulse Thereafter, as the slow down switch in the detector 70 isclosed through the actuation of the lever 66 and the senser 70a by the movement of the dog 63 in the course of the pulse driving rapid retraction, the detector 70 generates a signal for reducing the speed of the stopping motor 33. Subsequently, as the original position detecting switch in the detector 70 is closed by the actuation of the dog 63, the detector 70 generates an original position detecting Signal for stopping the pulse distribution to the stepping motor 33 and therefore, the wheel slide 13 or the grinding wheel 14 can be returned to and positioned at the original position thereof which is mechanically memorized by the dog 63 and the detector 70 independently of the electric control circuit.

In accordance with the present invention, the wheel slide 13 can be automatically and accurately returned to the original position for a grinding infeed and, the idling time in the course of the grinding operations can be minimized,

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the inventin may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A grinding machine comprising:

a bed;

workpiece supporting means mounted on said bed;

a wheel slide slidably mounted on said bed and rotatably supporting a grinding wheel driven by a motor thereon;

a hydraulic cylinder provided on said bed and serving to rapidly move said wheel slide toward and away from a workpiece on said workpiece supporting means;

a stepping motor mounted on said bed and serving to feed said wheel slide toward and away from the workpiece for grinding the same;

dressing means mounted on said wheel slide and being movable toward and away from said grinding wheel for dressing the same;

first feed means mounted on said wheel slide for feeding said dressing means toward said grinding wheel by a predetermined dressing amount whenever a dressing operation on said grinding wheel is performed;

second feed means mounted on said wheel slide for actuating said dressing means so as to perform a dressing operation on said grinding wheel;

said stepping motor further serving to move said wheel slide toward the workpiece by a distance corresponding to said predetermined dressing amount whenever the dressing operation is performed; and

original position determination means, having shiftable means slidably supported on said wheel slide, drive means connected to said first feed means for shifting said shiftable means by a distance corresponding to said predetermined dressing amount in a direction of retraction of said wheel slide whenever the dressing operation is performed, and detecting means mounted on said bed for detecting an original retracted position of said wheel side in cooperation with said shiftable means and generating a signal for serving to stop the retraction movement of said wheel slide when said wheel slide is retracted from said workpiece,

whereby said wheel slide can be accurately positioned at the original retracted position thereof which must be varied in accordance with a reduction of said grinding wheel caused by dressing operations thereon.

2. A grinding machine according to claim 1, further comprising switching means for selectively utilizing said signal serving to stop the movement of said wheel slide.

3. A grinding machine according to claim I, wherein said shiftable means comprises a shaft which is driven by said drive means connected to said first feed means in a direction of the retraction of said wheel slide by a distance corresponding to said predetermined dressing amount whenever the dressing operation is performed, and a dog member adjustably mounted on one end of said shaft, said dog member co-operating with said detecting means for determining said original position of said wheel slide.

4. A grinding machine according to claim 1, wherein said first feed means comprises an intermittent motion mechanism for feeding said dressing means toward said grinding wheel by said predetermined dressing amount in each dressing operationv 5. A grinding machine according to claim 1, wherein said detecting means comprises first and second switches for respectively generating a signal serving to reduce the speed of said wheel slide and a stopping signal serving to stop said wheel slide, when the same reaches the original position thereof, in co-operation with said shiftable means.

6. A grinding machine according to claim I, further comprising second detecting means for detecting an advancing end of said wheel slide in cooperation with said shiftable means.

7. A grinding machine according to claim 3, wherein said detecting means comprises a box mounted on said bed, a lever pivotally mounted on said box and being swingable by an engagement of the same with said dog member, and a detector fixedly mounted on said box and having a sensor contacting said lever.

8. A grinding machine according to claim 7, further comprising an adjustable member provided between said lever and said sensor for adjusting the distance therebetween.

9. A grinding machine according to claim 1, wherein said first feed means comprises an intermittent infeed mechanism, a worm connected to said intermittent infeed mechanism, a first worm wheel engaged with said worm, a first screw connected to said first worm wheel for feeding said dressing means in accordance with rotation of said first worm wheel, and said drive means comprises a second worm wheel engaged with said worm and second screw connected to and rotated by said second worm wheel. said second screw being engaged with said shiftable means for shifting the same in accordance with rotation of said feed screw,

10. A grinding machine according to claim 9, wherein said first and second worm wheels have the same diameter.

11. A grinding machine according to claim 10, wherein said first and second screws have the same thread pitch. 

1. A grinding machine comprising: a bed; workpiece supporting means mounted on said bed; a wheel slide slidably mounted on said bed and rotatably supporting a grinding wheel driven by a motor thereon; a hydraulic cylinder provided on said bed and serving to rapidly move said wheel slide toward and away from a workpiece on said workpiece supporting means; a stepping motor mounted on said bed and serving to feed said wheel slide toward and away from the workpiece for grinding the same; dressing means mounted on said wheel slide and being movable toward and away from said grinding wheel for dressing the same; first feed means mounted on said wheel slide for feeding said dressing means toward said grinding wheel by a predetermined dressing amount whenever a dressing operation on said grinding wheel is performed; second feed means mounted on said wheel slide for actuating said dressing means so as to perform a dressing operation on said grinding wheel; said stepping motor further serving to move said wheel slide toward the workpiece by a distance correspondiNg to said predetermined dressing amount whenever the dressing operation is performed; and original position determination means, having shiftable means slidably supported on said wheel slide, drive means connected to said first feed means for shifting said shiftable means by a distance corresponding to said predetermined dressing amount in a direction of retraction of said wheel slide whenever the dressing operation is performed, and detecting means mounted on said bed for detecting an original retracted position of said wheel side in cooperation with said shiftable means and generating a signal for serving to stop the retraction movement of said wheel slide when said wheel slide is retracted from said workpiece, whereby said wheel slide can be accurately positioned at the original retracted position thereof which must be varied in accordance with a reduction of said grinding wheel caused by dressing operations thereon.
 2. A grinding machine according to claim 1, further comprising switching means for selectively utilizing said signal serving to stop the movement of said wheel slide.
 3. A grinding machine according to claim 1, wherein said shiftable means comprises a shaft which is driven by said drive means connected to said first feed means in a direction of the retraction of said wheel slide by a distance corresponding to said predetermined dressing amount whenever the dressing operation is performed, and a dog member adjustably mounted on one end of said shaft, said dog member co-operating with said detecting means for determining said original position of said wheel slide.
 4. A grinding machine according to claim 1, wherein said first feed means comprises an intermittent motion mechanism for feeding said dressing means toward said grinding wheel by said predetermined dressing amount in each dressing operation.
 5. A grinding machine according to claim 1, wherein said detecting means comprises first and second switches for respectively generating a signal serving to reduce the speed of said wheel slide and a stopping signal serving to stop said wheel slide, when the same reaches the original position thereof, in co-operation with said shiftable means.
 6. A grinding machine according to claim 1, further comprising second detecting means for detecting an advancing end of said wheel slide in cooperation with said shiftable means.
 7. A grinding machine according to claim 3, wherein said detecting means comprises a box mounted on said bed, a lever pivotally mounted on said box and being swingable by an engagement of the same with said dog member, and a detector fixedly mounted on said box and having a sensor contacting said lever.
 8. A grinding machine according to claim 7, further comprising an adjustable member provided between said lever and said sensor for adjusting the distance therebetween.
 9. A grinding machine according to claim 1, wherein said first feed means comprises an intermittent infeed mechanism, a worm connected to said intermittent infeed mechanism, a first worm wheel engaged with said worm, a first screw connected to said first worm wheel for feeding said dressing means in accordance with rotation of said first worm wheel, and said drive means comprises a second worm wheel engaged with said worm and second screw connected to and rotated by said second worm wheel, said second screw being engaged with said shiftable means for shifting the same in accordance with rotation of said feed screw.
 10. A grinding machine according to claim 9, wherein said first and second worm wheels have the same diameter.
 11. A grinding machine according to claim 10, wherein said first and second screws have the same thread pitch. 